765 





Class _ 
Book 



COPYRIGHT DFPOSIT 



GUIDE 



TO THE 



Dissection and Study 



OF THE 



Cranial Nerves and 
Blood Vessels 



of 

The Horse 

BY 

GRANT SHERMAN HOPKINS 

New York State Veterinary College 

Ithaca, N. Y. 

SECOND EDITION 



<z 



^ 



GUIDE 



TO THE 



Dissection and Study 



OF THE 



Cranial Nerves and 
Blood Vessels 



OF 



The Horse 



SECOND EDITION 



COPYRIGHT I922 
SY GRANT SHERMAN HOPKINS 



THE CRANIAL NERVES. 



.Y.I.I// 


Real or 

Drip i I 


. 1 pparent or 

Superfu ial 

Oi igin 


Foramen of Exit 


h'liin Hon 


I X. olfactorius. 


Olfactory epithelium 


( llfactory bulb. 


Foramina in tin cribriform 
plate. 


Sensory. 


II. N. opticus. 


i ianglion i ells of the 
re1 ina 


Optii chi 


I'm. 1 1] iticum. 


:■ -'ii i 'i j 


III. X. oculomot' irius, 


Floor of the aqueduct 
of Sylvius. 


Crus cerel iri, 


I'm. lacerum orbitalc 


Motor. 


IV. X. trochlearis. 


Floor of the aqueduct 
of Sylvius. 


Anterior medul- 
lary velum. 


Fm. patheticum. 


Motor. 


| Motor 
1 root. 
V. X. trigeminus-! 

Sensi ty 
[ root. 


Floor of 4th ventricle 
and the pons. 

< ranglii hi semilunare. 
rion ganglion. ) 


Pons. J 
1 


Fm. lacerum bai is cranii, 

I'm. rotundum, 

Fm. lacerum orbitalc. 


i .I 
and 
Motor 


VI. X. abducens. 


Floor of 4th ventricle 

and 

gang. genieulat urn. 


Med, ,11a 


Fm. lacerum i irbitale. 


Motor. 


VII. N. facialis. 


Floor of 4th ventricle. 


Me lulla 


I'm i tj lomastoideum. 


Sensory 

and 
Motor. 


VIII. X. acusticus. 


Ganglion spirale and 
ganglion vestibulare. 


Medulla. 


Meatus acusticus internus. 


Sen :i in . 


IX. N. glossopharyngeus. 


Floor of 4th ventricle 
and the ganglion 
petrosum. 


Medulla. 


1 ; lacerum 1 >asis cranii. 


Sensory 

and 
Motor. 


X. X. vagus. 


Floor of 4th ventricle 
and the ganglia jug- 
ulare and nodosum. 


Medulla. 


Fm. lacerum basis cranii. 


Sensory 

and 
Motor. 


XI. X. accessorius. 


Fli ii ir of 4th ventricle 
and the spinal c ird 
as far back asthe6th 
or 7th spinal nerve. 


Medulla and 
cen ieal por- 
tion of spinal 
cord. 


cerum ba i ''rami. 


Motor. 


XII. X. hypoglossus. 


Floi ir of 4th ventricle. 


Medulla. 


Fm. hypogl i 


Motor. 



§T,!.A661564 



• i 



The Cranial Nerves and Blood Vessels 
of the Horse 

According to the usual enumeration there are twelve pairs of cranial nerves. 
The first or olfactory nerve, on either side, consists of numerous soft, gray, 
non-medullated fibers which are not united into a single nerve trunk but 
pass through the cribriform plate of the ethmoid bone as numerous small 
bundles; these several bundles taken together are considered as one nerve. 

Of the twelve pairs of cranial nerves three are sensory, viz., the olfac- 
tory, the optic and the acoustic nerves. Five are motor, viz., the oculo- 
motor, trochlearis, abducens, accessory and hypoglossal nerves. The remain- 
ing four nerves, viz., the trigeminal, facial, glossopharyngeal and vagus, are 
mixed nerves. 

The relation of the motor and the sensory nerves to the brain and spinal 
cord is radically different. The motor nerve fibers originate from nerve 
cells that lie within the gray matter of the brain and spinal cord and are 
distributed principally to the skeletal and visceral musculature. The sen- 
sory nerve fibers, on the other hand, originate from nerve cells that are 
situated in the sensory ganglia or the end organs lying wholly outside 
of the central nervous system. The sensory nerve fibers enter the brain 
and spinal cord and terminate either directly or indirectly in the respective 
sense areas and reflex centers of the central nervous system. Under normal 
conditions the motor fibers are stimulated only at their central origin, i. e., 
through the nerve cells in the brain and spinal cord from which the fibers 
originate. The sensory fibers are stimulated only at their endings in the 
peripheral tissues, the skin, the mucous membrane and the sense organs. 

Of the purely sensory nerves the first or olfactory originates from the olfac- 
tory cells of the nasal mucous membrane and passes in the form of numerous 
soft, gray, non-medullated fibers through the lamina cribrosa of the ethmoid 
to the olfactory bulb of the brain. The connections established by the 
nerve fibers that connect the olfactory bulb with the cerebral hemispheres 
are complicated and in part incompletely known. The optic nerve arises 
from the ganglion cells of the retina of the eye. From, these cells the nerve 
fibers pass through the optic nerve and thence to the primary optic centers 
of the brain. 



The origin of the acoustic nerve is from two ganglia in the internal ear. 
The acoustic nerve consists of two parts, the cochlear and vestibular branches. 
The cochlear branch arises from the ganglion spirale of the cochlea and 
the vestibular branch from the ganglion vestibulare of the internal ear. From 
these sensory ganglia of origin the nerve fibers pass through the internal 
acoustic meatus to their respective acoustic and equilibrium centers in 
the brain. 

The twelve pairs of cranial nerves as commonly enumerated are given in 
the preceding table. The part or region of the brain to which the respective 
nerves are attached is often spoken of as the place of origin of the nerve. 
It should be kept in mind, however, that the real origin of the respective 
motor nerves is from a group or nucleus of nerve cells situated within 
the central nervous system and that the real origin of the sensory nerves is 
from their respective ganglia or end organs situated outside of the central 
nervous system. The sensory fibers of the fifth, seventh, ninth and tenth 
cranial nerves originate from the cells of the ganglia of these nerves. A 
short distance from the ganglion nerve cells the sensory fibers divide into 
two branches of which one branch passes into the brain while the other 
passes to the peripheral tissues as the skin, mucous membrane, teeth, etc., 
the two branches together constituting a sensory nerve fiber. 



PREFACE 

This dissection guide is designed to meet the needs of the student for an 
orderly and systematic guide to the dissection of the cranial nerves and 
blood vessels. By exercising a little care nearly all of the parts may be 
left intact for study and demonstration after the dissection is completed. 
After completing the dissection of a part, as a nerve or blood vessel, which 
often must be done piecemeal, it is essential that the student get a compre- 
hensive idea of the structure as a whole. This idea should be got from 
the specimen itself. Most students need encouragement to study and 
to learn the actual object rather than to memorize text-book descriptions 
of it. Too often the student is unable to identify on the dissected specimen a 
given structure although he may be able to repeat practically everything 
that is said of it in the book. 

The dissection of the nerve supply to the larynx preferably should be done 
on another larynx. Otherwise the vessels and nerves already dissected, 
in this region of the head, will be so mutilated as seriously to interfere with 
their subsequent demonstration. 

After completing the dissection and study of the head the student should 
demonstrate his dissection. 

A satisfactory demonstration necessitates the presentation of visual 
evidence confirmatory of all oral statements. 



9 

will be dissected later. The nerves auricularis medius and auricularis 
posterior and also the three small nerves to the muscles digastricus, stylo- 
mandibularis, occipito-styloideus and stylohyoideus originate from the 
N. facialis at the stylomastoid foramen, PI. II, 52, 53, 57. The two auricular 
nerves are readily found but the other three small nerves are covered by a 
thin aponeurosis and cannot be demonstrated satisfactorily at present. 
Usually a nerve loop encircles the A. auricularis posterior, PL II, 58. 

N. auricularis posterior. 

Carefully remove the skin of the external ear. The N. auricularis pos- 
terior originates from the N. facialis at the stylomastoid foramen and accom- 
panies the peripheral portion of the A. auricularis posterior as shown in PL 
II, 52. The nerve, covered by the parotid gland, passes dorsally across the 
base of the styloid process of the occipital bone and is distributed to the pos- 
terior auricular muscles. Turn aside the overlying structures and trace 
the nerve as far as possible. 

A. auricularis posterior. PL II, 46. 

The superficial branches of this artery should now be dissected. The 
origin of the artery and its deep branch cannot be seen at this stage of the 
dissection. Of the two superficial branches the larger, posterior branch 
passes to the posterior part of the ear, near its base, and divides into two 
branches both of which extend to near the tip of the ear where they anas- 
tomose with each other; one of these anastomosing branches runs along 
near the middle of the posterior surface of the external ear and the other 
near the inner or medial border of the ear. 

The much smaller of the two superficial branches of the A. auricularis 
posterior passes along the lateral or external border of the ear and anas- 
tomoses with the middle branch. A small branch accompanies the N. 
auricularis medius through the foramen near the base of the styloid process 
of the conchal cartilage to the inner surface of the ear, PL II. 

N. auricularis medialis or internus. 

This nerve originates from the N. facialis close to the stylomastoid for- 
amen, PL II, 53. Surrounded by gland tissue, it passes along the styloid 
process of the conchal cartilage to the foramen near the base of this process 
through which the nerve passes to the inner surface of the ear. 

N. auricularis anterior or auriculo-palpebraris. 

This nerve, as already indicated, originates from the dorsal edge of the 
N. facialis immediately posterior to the V. temporalis superficialis, PL II, 54. 



10 

Transect and turn aside the thin M. zygomatico-auricularis and carefully 
remove the gland tissue which surrounds the nerve. Before the nerve 
crosses the zygomatic process of the temporal bone it gives off several small 
branches which supply the anterior auricular muscles. 

The main portion of the N. auricularis anterior passes anteriorly across 
the zygomatic process of the squamous temporal bone a little posterior to 
the mandibular articular surface; here it intermixes somewhat with a 
branch of the N. lacrimalis, from the 5th cranial nerve, and with it forms a 
plexus known as the plexus auricularis anterior, PI. II, 55. The larger 
portion of the nerve, however, continues anteriorly to the inner canthus of 
the eye and is distributed to the muscles corrugator supercilii, orbicularis 
palpebrarum and levator naso-labialis. (The branch to the last mentioned 
muscle may be traced 10 to 15 cm. below the eye). The branch of the N. 
lacrimalis which helps to form the plexus auricularis anterior passes through 
a small groove on the zygomatic process of the temporal bone immediately 
posterior to the suture between this process and the supraorbital process of 
the frontal bone and is distributed to the skin at the base of the ear. 

Ramus colli. 

This small nerve arises from the N. facialis almost directly opposite the 
N. auricularis anterior, PI. II, 59, or occasionally in common with the 
anterior end of the nerve loop encircling the A. auricularis posterior. It 
passes obliquely through the parotid gland and then extends along its sur- 
face, close to the V. jugularis, immediately beneath the aponeurosis which 
covers the superficial face of the gland. The M. parotido-auricularis 
receives a filament either from the ramus colli or directly from the N. facialis. 
The ramus colli receives communicating branches from the second to the 
sixth spinal nerves. 

The parotid gland should now be removed in order to expose the small 
nerves to the muscles occipito-styloideus, digastricus, stylo-mandibularis 
and stylohyoideus. In removing the gland, if the handle of the scalpel 
be used pretty largely the danger of injury to the veins and underlying 
structures will be greatly diminished. Interposed between the deep face 
of the parotid gland and the subjacent structures is an aponeurosis which 
is attached principally to the tendons of the sterno-mandibularis and brach- 
iocephalicus. The three small nerves to the muscles occipito-styloideus, 
digastricus, stylo-mandibularis and stylohyoideus originate from the 
ventral edge of the N. facialis, near the stylomastoid foramen. The 
filament to the M. stylohyoideus can not be readily demonstrated until 
after the removal of the mandible. 



Dissection of the Cranial Nerves and Blood Vessels 

Make an incision in the skin on the median plane from near the free 
margin of the lower lip to a point opposite the third or fourth tracheal 
ring. The anterior end of this incision should now be continued dorsally 
along the margin of the lips as far as to the median plane of the upper 
lip. A second incision should now be made from the tip of the ear along 
its lateral margin to its base; continue this incision along the parotid 
gland and prolong it to the first incision. Reflect the skin. Care should be 
taken in reflecting the skin not to include the thin M. cutaneous faciei. 
This muscle is fairly well defined in the submaxillary space and on the lateral 
face of the horizontal portion of the mandible (PI. I, I9;P1. II, 17) but the portion 
which covers the greater part of the M. masseter is largely aponeurotic. 
Upon the removal of the skin two large branches of the N. facialis will be 
seen extending across the M. masseter, covered only by the thin M. cuta- 
neous faciei. To dissect this latter muscle, begin at its more or less clearly 
defined border in the submaxillary space and dissect it from the underlying 
parts. This may be done the more readily if the muscle be transected a little 
posterior to the large nerve which is supplied to it and the overlying skin 
by one of the branches of the N. facialis (PI. I, nerve just below 36). Over 
a large part of the M. masseter the cutaneous faciei is mostly aponeurotic 
and this portion of the muscle may be entirely removed. 

N. facialis, VII. Mixed. 

This nerve is usually classed as a mixed nerve. The facial nerve proper, 
however, is purely motor at its nucleus of origin in the dorsal part of the 
pons. The nerve emerges from the base of the brain immediately caudal to 
the pons, PL VI, 14. 

The N . facialis passes from the cranial cavity through the internal acoustic 
meatus and the facial canal of the petrous temporal bone. Closely associated 
with the facial nerve in its course through the facial canal are a sensory nerve— 
N. interm edius^and a ganglion— Gang, geniculatum— which are often regarded 
as the sensory part of the facial nerve. This sensory nerve and ganglion 
however have no nerve connection with the facial nerve and form no integral 
part of it. The nerve fibers from the geniculate ganglion to the brain 
constitute the nerve intermedius; the peripheral fibers from the ganglion 



large nerve with which the N. labialis dorsalis intermixes some distance 
anterior to the infraorbital foramen is the N. infraorbi talis, a branch of the 
5th cranial nerve. 

Before proceeding farther with the dissection of the nerves the following 
structures should be demonstrated. 

Submaxillary lymph gland. 

Remove the connective tissue from the submaxillary space and note the 
location, form and size of the submaxillary lymph gland. The gland is V 
shaped, each arm being from 10 to 12 cm. in length. 

Parotid duct and the V. maxillaris externa. 

Trace the V. maxillaris externa to the place where it passes from the 
submaxillary space across the border of the mandible. Refer to PL II for 
an idea of the relations of the parotid duct, the artery and the vein shortly 
after they cross the margin of the mandible. At this stage of the 
dissection, veins 28, 29, 30, 31 cannot be seen, as they are covered by the M. 
masse ter; they will be exposed later. Cut the two branches of the N. facialis 
(dorsal and ventral labial nerves) about 5 cm. anterior to the parotid gland and 
reflect them from the M. masseter. Now continue the dissection of the parot- 
id duct and the adjacent portions of the A. and V. maxillaris externa. 
Trace the parotid duct to its termination in the oral cavity opposite the third 
superior premolar tooth. Note that the duct is somewhat enlarged just 
before it opens into the oral cavity. Demonstrate by inserting a probe into 
the duct a few centimeters from its termination. 

A. labialis ventralis or inferior. 

This artery originates from the A. maxillaris externa about 2 cm. ventral to 
the M. depressor labii inferior, PI. 1 1, 40; PI. VII, 10. It passes obliquely across 
the deep face of this muscle and continues to the lower lip where it anastomoses 
with its fellow of the opposite side. It gives off a branch to the angle of the 
mouth (A. anguli oris) which may anastomose with the A. labialis superior. 
The A. labialis inferior supplies the M. depressor labii inferior, the inferior 
molar glands and the lower lip and skin of this region. 

A. labialis dorsalis or superior. 

The A. labialis superior is the next large branch of the A. maxillaris 
externa. It originates near the level of the maxillary or facial crest, PI. I, 
37; PI. II, 41. It passes beneath the muscles zygomaticus, levator naso- 
labial and dilator naris lateralis all of which have previously been turned 
aside. Trace the artery into the upper lip and demonstrate its anas- 



13 



tomosis with its fellow of the opposite side; and also its anastomosis with 
the palatine arteries, by means of a branch which passes through the foramen 
incisivum of the premaxilla, PI. VII, 16. 

A. lateralis nasi. 

This vessel arises from the maxillaris externa a little penpheral to the 
A labialis superior, PI. II, 42. It extends nearly parallel to the A. labiahs 
superior and enters the nasal fossa near the angle formed by the nasal and 
premaxillary bones. 

Aa. dorsalis nasi and angularis oculi. 

These two small vessels may be considered as the terminal branches of the 
A maxillaris externa. They arise on the M. levator labii supenons pro- 
prius and pass under the M. levator nasolabialis, the first to the dorsum 
nasi and the second to the vicinity of the inner canthus of the eye. 

A. & V. transversa faciei, PI. I, 32, 33; PI- n > 3*. 4§- 

Note the relation of this artery and vein to the zygomatic process of the 
temporal bone and to the facial crest. Note also the small nerve which 
accompanies the superficial portion of the artery and vein; this small nerve 
is a branch of the N. temporalis superficialis, as will be demonstrated later. 
After a short course the artery and vein dip into the M. masseter, a portion 
of which must be removed in order to demonstrate the course of the vessels, 
PI II 31, 48. Just after the A. transversa faciei crosses the posterior 
border of the mandible and gains its lateral face, it gives off a deep branch 
which, accompanied by a large vein, passes ventrally between the bone and 
the deep face of the M. masseter (PI. II, immediately below 61 ) . To expose 
the vessels just mentioned and also the N. massetericus, proceed as follows: 
Reflect the proximal portion of the N. facialis from the M. masseter and 
remove enough of the muscle to expose for a distance of 2 or 3 cm. the 
deeply situated branches of the A. & V. transversa faciei. The N. mas- 
setericus is deeply embedded in the muscle and lies from 3 to 4 cm. anterior 
to the vessels just exposed, PI. II, 63. To uncover the nerve, make an 
incision 8 to 10 cm. in length and about one and one-half centimeters m 
depth, in the M. masseter just ventral of, and parallel to, the A. & V. trans- 
versa 'faciei and carefully turn aside the overlying portion of the muscle 
until the nerve is uncovered. Demonstrate the distribution of the nerve to 
the M. masseter and then cut it 5 to 8 cm. from the sigmoid notch of the 
mandible. (The origin of the nerve from the mandibular division of the 
5th cranial nerve cannot be demonstrated until after the removal of the 
mandible, PL III, 62). The dissection of the deep branches of the A. & V. 



'4 

transversa faciei, already partially exposed, should now be completed. The 
artery almost immediately divides into two branches of which the larger is 
distributed to the M. masseter. The smaller branch is covered by the vein 
and can be traced for only a short distance, at present. It runs beneath 
the V. transversa faciei and the zygomatic process of the temporal bone, 
enters the temporal fossa and anastomoses with the A. temporalis posterior. 
Each of the above mentioned arterial branches is accompanied by a vein. 

A. & V. masseterica. 

The V. masseterica joins the jugular opposite the V. auricularis posterior, 
PI. II, 35. It is formed, at the posterior border of the mandible, by two 
branches one of which comes from the M. masseter and the other from the 
M. pterygoideus interims. Trace the masseteric branch and its accompanying 
artery as far as possible. The vein usually anastomoses with the V. bucci- 
natoria. The origin of the A. masseterica and the pterygoid branch of 
the vein will be demonstrated after the mandible is removed. The M. 
masseter should now be removed as shown in PI. II, but in doing this be 
careful not to injure the large veins which lie beneath the muscle, PI. II, 29, 
30. These vessels, Vv. buccinatoria and alveolaris, and also the small 
artery that lies just dorsal to the V. buccinatoria, should be cleaned up as 
shown in PI. II. 

N. ramus transversus faciei. 

This small nerve accompanies the A. & V. transversa faciei, as already 
demonstrated. Trace the nerve to its place of origin from the N. temporalis 
superficialis, PI. Ill, 74. At this stage of the dissection the latter nerve 
usually is not clearly distinguishable from the N. facialis, as the two nerves 
unite at the place of origin of the ramus transversus faciei and also from this 
point to its place of origin the N. temporalis superficialis is covered by the 
sum nmding structures. 

Removal of the mandible. 

Cut the A. & V. maxillaris externa, the parotid duct, the A. & V. trans- 
versa faciei, and the A. & V. masseterica at their respective places of crossing 
the margin of the mandible. All of the horizontal portion of the mandible, 
except the part anterior to the mental foramen, should now be completely 
denuded as follows: Begin at the ventral margin of the horizontal portion 
of the mandible and dissect up en masse all of the overlying structures so that 
when these are turned dorsally both the upper and lower rows of teeth are 
exposed. With the saw and chisel cut the ramus of the mandible a little 



15 

posterior to the mental foramen and also cut it near the place of crossing of 
the N. facialis. With strong plyers abduct the ramus of the mandible just 
enough to expose the artery, vein and large nerve that enter the mandibular 
foramen. All three of these structures should now be cut. Note the small 
N. mylohyoideus, PI. Ill, 72, which lies just posterior to the above men- 
tioned vessels and nerve, and close to the surface of the bone. Continue to 
abduct the mandible and at the same time detach from it, as completely as 
possible, the muscles pterygoideus internus and stylomandibularis ; also 
transect the M. mylohyoideus near its attachment to the mandible. Detach 
the M. digastricus from the ramus of the mandible and remove the latter. 
The remaining proximal portion of the mandible, i. e., the coronoid process 
and the condyle, are best removed by first detaching, with saw and chisel, the 
coronoid process from the condyle, but in doing this some care is necessary 
not to injure the N. massetericus, which passes through the corono-condyloid 
or sigmoid notch. Now cut the M. pterygoideus externus close to its attach- 
ment to the mandible and disarticulate and remove the condyle. The 
zygomatic arch and the coronoid process of the mandible should now be 
removed. With saw and chisel cut the zygomatic process of the temporal 
bone near the middle of the condyle and glenoid fossa and at right angles to 
their long axis; cut the orbital process of the frontal bone just peripheral to 
the supraorbital foramen and also the malar bone at the level of the maxillary 
tuberosity of the maxilla. Sever the palpebrae and the periorbita or orbital 
sheath, to within about 2 cm. of the inner canthus, from their attachments to 
the rim of the orbit, taking care not to cut the nerve and artery that pass 
through the supraorbital foramen. Remove the detached portion of the 
zygomatic arch and also the coronoid process of the mandible; in removing 
the latter, however, disturb as little as possible the overlying plexus auricu- 
laris anterior and the M. temporalis, whose insertion completely surrounds 
the coronoid process. Slit the M. temporalis down to the bone and care- 
fully detach the muscle from the coronoid process and remove the latter. 

Before proceeding with the dissection of the nerves, the large V. maxil- 
laris interna and certain other veins should be noted. 

V. masseterica (continued). 

The deep branch of this vein should now be traced into the M. pterygoi- 
deus internus. 

A little peripheral to the points where the veins masseterica and auricu- 
laris posterior open into the V. jugularis, the latter vessel is formed by the 
union of two large branches, the V. temporalis superficialis and the V. 
maxillaris interna, PL II, 37, 38. 



16 

V. temporalis superficialis. 

The V. temporalis superficialis is formed by the union of the veins au- 
ricularis anterior and transversa faciei. The course of the vein and its 
relation to the N. facialis are shown in PL II, 37. Occasionally the N. facialis 
lies superficial to the temporal vein. 

V. auricularis anterior. 

This vein arises from the anterior face of the external ear and unites with 
the transversa faciei to form the V. temporalis superficialis. Demonstrate 
the large branch, V. cerebralis dorsalis, which emerges from the parieto- 
temporal canal posterior to the postglenoid process of the squamous tem- 
poral bone, and joins the auricularis anterior shortly before the latter unites 
with the transversa faciei. 

The V. transversa faciei has already been traced. 

V. maxillaris interna. 

Trace the large V. maxillaris interna, PL II, 38, from the V. jugularis 
along the ventral border of the M. pterygoideus externus. At the alveolar 
border of the mandible it makes an abrupt S shaped curve and is continued 
by the large V. buccinatoria, PL II, 29. The principal radicles of the V. 
maxillaris interna are as follows: 

(1) V. temporalis profunda. This is a large vessel which receives smaller 
branches from the M. temporalis and from the parieto-temporal canal. Its 
dissection should be deferred until after the temporal nerves have been 
dissected. 

(2) V. dorsalis linguae. This large vein is a satellite of the N. lingualis; 
it enters the V. maxillaris interna near the alveolar margin of the mandible. 

(3) V. buccinatoria, PL II, 29. This is the direct continuation of the 
V. maxillaris interna, as mentioned above. It may communicate with the 
V. alveolaris in the vicinity of the maxillary tuberosity. Its communication 
with the V. maxillaris externa is shown in PL II. 

(4) V. alveolaris, PL II, 30. Push aside the orbital fat and trace the 
vein to the periorbita. Its connection with the ophthalmic vein cannot 
be seen until after the periorbita has been removed. 

Venae labiales, PL II, 25, 26, 27, 2H. 

Trace the V. labialis communis (PL II, 25) from its place of union with 
the maxillaris externa to the venous plexus near the middle of the cheek. 
From this plexus, trace the respective labial veins to the lips; also trace the 
branch which communicates with the V. buccinatoria as shown in PL II, 28. 
In tracing the latter do not cut the nerve which lies in close proximity to the 
dorsal surface of the vein, PL II, 65. 



i7 

V. angularis oculi, V. dorsalis nasi and V. lateralis nasi. PI. I, 27, 28, 29. 

These branches have already been exposed while tracing the correspond- 
ing arteries. 

Cut the various veins that enter the maxillaris interna and turn aside or 
remove the latter. 

N. trigeminus, V. Mixed. 

The apparent origin of the N. trigeminus is from the side of the pons by 
two roots, of which the larger is sensory and the smaller motor; the fibres of 
the sensory root, however, really originate from the large ganglion semilunare 
of the 5th cranial nerve. The fibers of the smaller motor root originate 
in the pons and mid brain. Within the cranial cavity, the trunk of the N. 
trigeminus divides into three large branches or divisions, viz., the N. oph- 
thalmicus, the N. maxillaris and the N. mandibularis, PI. VI, 12', 12", 12"'. 
All of the nerve fibres of the motor root enter the N. mandibularis; a large 
number of sensory fibres also enter this portion of the 5th nerve thus making 
it a mixed nerve. The ophthalmic and maxillary divisions of the trigeminus 
are purely sensory nerves. The N. ophthalmicus passes from the cranial 
cavity through the foramen lacerum orbitale; the N. maxillaris passes 
through the foramen rotundum and the N. mandibularis through the fora- 
men lacerum basis cranii. 

N. mandibularis. Mixed. 

The N. mandibularis is made up of both sensory and motor nerve fibres. 
The nerve, which has a very short course, leaves the cranial cavity by the fo- 
ramen lacerum basis cranii and, under cover of the M. pterygoideus ex- 
ternus, divides into several terminal branches as shown in PL III, 61. To 
demonstrate these branches of the N. mandibularis first identify the two 
large nerves, N. lingualis and N. alveolaris inferior, PI. Ill, 69, 71, which 
extend across the outer surface of the M. pterygoideus internus, and trace 
them towards the base of the skull as far as to the edge of the M. pterygoideus 
externus from beneath which the two nerves emerge. The M. pterygoide- 
us externus must not be removed but simply pushed aside just sufficiently to 
expose clearly the origin of the nerves. 

Branches of the N. mandibularis. 

(1) N. alveolaris inferior. Sensory. 

This nerve arises from the N. mandibularis in common with the N. 
lingualis, PI. Ill, 69, 71. It passes through the alveolar canal of the man- 
dible and upon emerging at the mental foramen it divides into several 
branches known as the mental nerves, which are distributed to the chin and 



i8 

the lower lip, PI. II, 64a. With a chisel, expose the nerve, artery and vein 
alveolaris inferior in their course through the alveolar or mandibular canal. 
As already mentioned, the Nn. mentales are simply the terminal branches 
of the N. alveolaris inferior. Trace them into the lower lip. Just before 
emerging from the mental foramen the N. alveolaris inferior gives off a 
branch that extends through a small osseous canal to the roots of the canine 
and incisor teeth. To demonstrate this small branch, medisect the lip and 
chin and remove the one half from their attachment to the mandible and 
turn them aside. Now carefully chisel away the bone and trace the nerve 
to the roots of the teeth. 

(2) N. mylohyoideus. 

This small nerve was noted when removing the mandible. Trace it to 
its origin from the N. mandibularis and to its termination in the M. mylo- 
hyoideus, the anterior portion of the M. digastricus and the skin of the 
anterior part of the submaxillary space, PI. Ill, 72. The filament to the 
M. digastricus is given off near the posterior border of the M. mylohyoideus. 

The N. mylohyoideus may appear to originate from the N. alveolaris 
inferior; the fibres, however, can readily be separated from this nerve and 
traced back to the N. mandibularis. 

Gl. sublingualis. 

Reflect the M. mylohyoideus and identify the sublingual salivary gland, 
PL III, 35; PI. VIII, fig. 1,8. It is from 12 to 15 cm. in length and from 
2 to 3 cm. in width. Note the sublingual crest and the 20 to 30 small 
openings of the ducts of the sublingual gland. 

(3) N. lingualis. Sensory. 

The N. lingualis arises from the mandibularis in common with the N. 
alveolaris inferior, PI. Ill, 69. The two nerves pass between the muscles 
pterygoideus externus and internus and soon diverge from each other, the 
lingual nerve lying to the inner side and somewhat anterior to the N. alveo- 
laris inferior. Near the place where the N. lingualis diverges from the 
alveolaris inferior, it is joined by the chorda tympani, a small nerve which 
originates within the facial canal of the petrous temporal, from the genicu- 
late ganglion of the N. intermedius. Demonstrate as much of the chorda 
tympani as possible. At the anterior border of the M. pterygoideus in- 
ternus the lingual nerve passes between the muscles mylohyoideus and 
styloglossus between which it extends as far as to the posterior end of the 
sublingual salivary gland where it passes beneath the gland and the M. sty- 
loglossus deep into the tongue. Dissect up the ventral edge of the sublingual 



19 

gland and turn it dorsally. Trace the nerve to the point where it dips be- 
tween the muscles styloglossus and genioglossus. Further dissection should 
be deferred until after the N. sublingualis has been dissected. The N. lingual - 
is gives off several small branches to the region of the maxillary tuberos- 
ity, PI. III. 

(4) N. sublingualis. Sensory. 

This small nerve arises from the dorsal edge of the N. lingualis opposite, 
or a few centimeters from, the anterior edge of the M. pterygoideus internus, 
PI. Ill, 70. Upon reaching the sublingual gland the nerve dips beneath it 
and accompanied by the sublingual artery and vein and the duct of the sub- 
maxillary salivary gland, all of which should now be studied, runs the whole 
length of the sublingual gland and terminates in the mucous membrane 
of the anterior portion of the floor of the mouth. Numerous small branches 
are given off from the N. sublingualis to the mucous membrane of the tongue 
and oral cavity. Demonstrate the termination of the submaxillary duct 
at the caruncula sublingualis. 

The N. lingualis, after giving off the sublingual, passes between the mus- 
cles mylohyoideus and styloglossus to the posterior extremity of the sub- 
lingual gland, as already mentioned. Here it turns obliquely across the 
ventral border of the M. styloglossus and extends along the inner surf ace of 
the muscle to the tip of the tongue. Demonstrate the numerous branches 
given off from the dorsal edge of the lingual nerve in its course between the 
muscles of the tongue. These branches extend to the mucous membrane of 
the anterior two-thirds of the dorsum of the tongue. 

(5) N. massetericus (continued). 

This nerve should now be traced from the point where it was cut, 5 to 8 
cm. from the sigmoid notch of the mandible, to its place of origin from 
the N. mandibularis, close to the base of the skull, PI. Ill, 62. From its 
place of origin it extends laterally, immediately anterior to the temporo- 
mandibular surface of the temporal bone and through the sigmoid notch of 
the mandible as already noted. 

Near its origin it usually gives off two branches, the Nn. temporales 
profundi, both of which should be traced into the temporal muscle, PI. Ill, 
63. The mass of fatty tissue in the orbit should now be removed after first 
demonstrating the small artery supplied to it. 

(6) N. buccinatorius. Sensory. 

The N. buccinatorius may be readily found at the antero-internal surface 
of the V. buccinatoria, PI. II, 65. Opposite the last molar tooth the nerve 



20 

passes between the M. depressor labii inferioris and the mucous membrane 
of the cheek and accompanies the inferior labial artery and vein to the lower 
lip. In this part of its course numerous branches are given off to the inferior 
molar glands and to the mucous membrane of the cheek and lower lip; one 
or more small branches may be traced to the upper lip in the immediate 
vicinity of the commissure. Now trace the nerve toward its place of origin 
from the N. mandibularis. Opposite the maxillary tuberosity it gives off 
several small branches to the superior molar glands and to the mucous mem- 
brane of the cheek. The N. buccinatorius passes between the maxillary 
tuberosity and the anterior border of the M. pterygoideus externus and 
thence through the M. pterygoideus externus which must be divided longi- 
tudinally in order to expose the nerve; do not, however, disturb the muscle 
more than is necessary clearly to expose the nerve, PI. Ill, 64. 

(7) N. temporalis profundus anterior. 

This small nerve originates from the N. mandibularis. It lies on the 
dorsal surface of the N. buccinatorius along which it extends to near the 
anterior border of that portion of the M. pterygoideus externus which is 
dorsal to the nerve, PI. Ill, 8. It then bends dorsally, as shown in PL III, 
65, and immediately enters the temporal muscle. 

(8) N. pterygoideus externus. 

This small nerve originates from the N. mandibularis and almost im- 
mediately enters the inner or deep surface of the external pterygoid muscle. 
Very frequently the nerve consists of two nearly parallel portions, PL III, 
67. 

(9) N. pterygoideus internus. 

The nerve to the M. pterygoideus internus is much larger than the one 
to the M. pterygoideus externus. It originates from the N. mandibularis and 
is partly covered by the dorsal edge of the common trunk of the nerves 
lingualis and alveolaris inferior. The nerve enters the muscle at its posterior 
border, PL III, 68. 

(10) N. temporalis superficialis. Sensory. 

This is a large sensory branch which originates from the N. mandibularis 
and joins the facial nerve at the posterior border of the mandible, PL III, 
74. It gives off several small branches one of which, ramus transversus 
faciei, accompanies the artery and vein of the same name for some distance 
across the M. masseter as has already been demonstrated; one small branch, 
ramus auricularis, accompanies the anterior auricular artery and vein to 
the ear. Numerous small filaments go to the parotid gland and to the 
external ear. 



N. ophthalmicus. Sensory. 

The N. ophthalmicus is the smallest of the three principal branches of the 
N. trigeminus. It originates from the semilunar ganglion and, for a short 
distance, is closely joined to the N. maxillaris but within the orbital hiatus 
the two trunks are separated by the thin osseous plate that separates the 
foramen lacerum orbitale from the foramen rotundum. Within this os- 
seous canal the nerve divides into three branches, viz., N. lacrimalis, N. 
frontalis or supraorbitalis, and the N. nasociliaris, all of which are sensory. 

To expose the nerve proceed as follows: With the handle of the scalpel, 
free from its attachment to the bone the portion of the temporal muscle that 
intervenes between the orbit and the M. pterygoideus externus, taking care 
not to break the artery that emerges from the temporal foramen; also simi- 
larly detach the portion of the M. pterygoideus externus that is attached 
to the region between the orbital hiatus and the alar or pterygoid foramen. 
Slit open the periorbita a little posterior to its point of connection with the 
V. alveolaris. Note on a prepared skull the relations to each other of the 
foramen patheticum, the foramen lacerum orbitale and the foramen rotun- 
dum. With a small chisel carefully remove enough of the bony plate that 
forms the lateral wall of the orbital hiatus to expose clearly the Nn. ophthal- 
micus and maxillaris; care should be taken not to disturb the small N. 
trochlearis which emerges from the foramen patheticum. Upon drawing 
aside the periorbita three nerves are visible, viz., the lacrimalis, the frontalis 
or supraorbitalis and the orbitalis. 

[The N. orbitalis is a branch of the N. maxillaris and will be dissected 
with that nerve.] 

(1) N. lacrimalis, Sensory. PI. IV, 27. 

This consists of several small branches which pass directly to the lacrimal 
gland and the upper eyelid. One of the larger branches, however, pierces 
the periorbita, passes posterior to the orbital process of the frontal bone and 
helps to form the plexus auricularis anterior. This branch of the N. lacri- 
malis supplies filaments to the skin of the temporal region and the base of the 
ear, as already noted when dissecting the N. auricularis anterior. 

(2) N. frontalis. Sensory. 

This nerve is of about the same size as the lacrimal and for some distance 
from its origin lies immediately dorsal to the N. lacrimalis, PI. IV, 25. 
Within the orbit it is enclosed by the periorbita until within 2 to 4 cm. 
of the supraorbital foramen when it pierces the periorbita and then lies 
b tween this membrane and the bone, PI. IV. After passing through the 



supraorbital foramen the nerve divides into several small branches which 
join with the terminal filaments of the N. auricularis anterior, and are dis- 
tributed to the skin of the forehead and upper eyelid. 

(3) N. nasociliaris. Sensory, PI. IV, 26; PI. V, 28. 

The N. nasociliaris has the same general course as the A. ophthalmica 
and lies close to either the dorso-lateral or convex side, PL V, 28, or fre- 
quently at the concave side of the artery. At its origin it is covered by the 
Nn. lacrimalis and frontalis. To expose the nerve, dissect up the muscles 
rectus dorsalis and levator palpebrae dorsalis and transect them at about 
one or two centimeters from their attachment to the globe of the eye, PI. V, 
7, 8. Beneath the M. rectus dorsalis the nerve divides into two main 
branches, PI. V, 29, 30, of which one branch, N. ethmoidalis, accompanies 
the ophthalmic artery through the ethmoid foramen into the cranial cavity 
and thence passes through the cribriform plate and is distributed to the 
mucous membrane of the nasal fossa. The other branch, N. infratrochlearis, 
is of about the same size as the ethmoidal branch. It extends along the 
ventral surface of the M. trochlearis or obliquus dorsalis as far as to the 
trochlea or pulley through which the muscle passes. Before attempting to 
trace the nerve farther first expose the terminal tendon of the muscle troch- 
learis or obliquus dorsalis and transect it close to the trochlea. The nerve 
may now readily be traced to the nasal canthus of the eye where it is distrib- 
uted to the skin, the membrana nictitans and the lacrimal apparatus in this 
region. Some of the filaments extend several centimeters beyond the nasal 
canthus of the eye. A small branch extends from the N. nasociliaris to the 
ciliary ganglion constituting the long or sensory root of the ganglion (radix 
longa ganglii ciliaris), PI. V, 32. 

N. maxillaris. Sensory. 

The origin of this division of the trigeminus from the semilunar ganglion 
of the fifth cranial nerve and its position immediately ventral to the N. 
ophthalmicus have already been noted. Carefully free the nerve and adjoin, 
ing arteries, PL IV, 30, and PL V, 25, of surrounding fatty tissue noting mean- 
time the three or four small nerves extending to the region of the max- 
illary tuberosity. The N. maxillaris divides into three branches, viz., 
N. orbitalis, N. infraorbitalis, and N. sphenopalatinus. 

(1) N. orbitalis. Sensory, PL IV, 28. 

The nerve orbitalis arises from the N. maxillaris before the latter passes 
through the foramen rotundum. It enters the periorbita or ocular sheath 



23 

and soon divides into two or more branches which extend between the 
periorbita and the M. rectus externus to the lateral canthus of the eye and are 
distributed to the lower eyelid. 

(2) N. infraorbitalis. Sensory. 

The N. infraorbitalis is simply the continuation of the greater portion of 
the N. maxillaris through the infraorbital canal. With saw and chisel 
expose the nerve by opening the maxillary sinus and the osseous canal 
through which the nerve passes. At the infraorbital foramen the nerve 
divides into three portions, a dorsal, a middle and a ventral, PI. II, 68, 69, 
70. The small dorsal portion, N. nasalis dorsalis or N. nasalis externus, 
consists of one or more branches which accompany the M. levator labii 
superiorus proprius and are distributed to the skin on the dorsum of the nose 
and the nasal diverticulum. The middle portion, N. nasalis anterior, is 
much larger than the preceding. It enters the anterior portion of the nasal 
fossa usually by two branches as shown in Plate II. The smaller of these 
two branches is distributed to the mucous membrane of the anterior part of 
the nasal fossa; the larger branch is continued to the skin of the upper lip. 
The ventral portion, ramus labialis dorsalis, is the largest of the three por- 
tions. It divides into numerous branches which intermix with the fibres of 
the N. labialis dorsalis of the facial nerve and are distributed to the skin and 
tactile hairs of the upper lip. The small branch, ramus alveolaris maxillae 
incisivus, supplied to the canine and incisor teeth, arises from the N. infra- 
orbitalis in the anterior part of the infraorbital canal. Two to four centi- 
meters before reaching the infraorbital foramen the ramus enters a small 
canal in the superior and premaxillary bones and runs in this canal to the 
roots of the canine and incisor teeth. With a small chisel expose the nerve 
throughout its intraosseous course, or see laboratory specimen already 
exposed. The small nerves to the maxillary sinus and the superior molar 
teeth also arise from Nn. maxillaris and infraorbitalis. Transect the N. 
infraorbitalis near its entrance to the infraorbital canal and turn aside the 
proximal part. 

(3) N. sphenopalatine. Sensory. 

The N. sphenopalatinus arises as a large somewhat flattened nerve from 
the ventral side of the N. maxillaris and passes directly to the sphenopalatine 
foramen, PL V, 41. Closely attached to the dorso-medial surface of the 
nerve are numerous ganglia (ganglia sphenopalatina or Meckel's ganglion) 
which are scattered along the nerve for a distance of 2 to 4 cm, PI. V, 42. 
A magnifying glass may be necessary to bring out clearly these small ganglia. 



24 

Note the numerous small filaments, a score or more, extending from the 
dorsal side of the ganglia to the periorbita. Some of these filaments pass 
through the periorbita to the structures within. Numerous filaments from 
the sphenopalatine ganglia join the Nn. sphenopalatine, palatinus major 
and palatinus minor. Immediately after passing through the sphenopala- 
tine foramen the N. sphenopalatinus divides into two nearly equal branches, 
a lateral or external branch and a medial or internal branch (see laboratory 
specimen). The lateral branch runs along the inferior turbinated bone and 
is distributed to its mucous membrane and to that of the middle and ventral 
nasal meati. The medial branch, N. septi narium, leaves the main trunk at 
nearly a right angle and passes to the posterior end of the nasal septum and 
then extends anteriorly towards the prenares. It lies near the ventral edge 
of the nasal septum and is distributed to the mucous membrane of the septum 
and also to the mucous membrane of the anterior portion of the hard palate . 

(4) N. palatinus anterior or major. Sensory. 

This large nerve arises from the N. sphenopalatinus and accompanies 
the anterior palatine artery through the palatine canal and groove, PI. 
V, 43. Expose from within the maxillary sinus the nerve and artery in 
their course through the palatine canal. In the palatine groove the nerve 
forms a kind of plexus around the artery. It is distributed principally to 
the mucous membrane of the hard palate but also sends some filaments 
through small foramina in the bones of the hard palate to the mucous mem- 
brane of the nasal fossa. 

(5) N. palatinus posterior or minor. 

This small nerve arises from the ventral edge of the sphenopalatine nerve 
in common with some of the fibres of the N. palatinus anterior. It passes 
through the groove formed by the maxillary tuberosity and the palatine 
bone and is distributed to the soft palate, PI. V, 44. 

N. canalis pterygoidei (Vidii). 

First demonstrate on a cleaned skull the two foramina of the pterygoid 
or vidian canal. Now lift up the A. maxillaris interna and the N. spheno- 
palatinus a little from the bone and note the vidian nerve extending from the 
anterior foramen of the canal to the posterior part of the sphenopalatine 
ganglion. (The N. canalis pterygoidei is formed by the union of ths supar- 
ficial petrosal branch of the N. facialis with a sympathetic filament). 



25 

Summary of the Branches of the N. Trigeminus or 5/// Cranial Nerve 

The N. trigeminus divides into three principal branches, viz., the N. 
ophthalmicus, the N. maxillaris and the N. mandibularis. The first two 
are sensory and the last is a mixed nerve. The N. mandibularis supplies the 
muscles of mastication, viz., the masseter, the temporal and the two ptery- 
goids; also the mylohyoid and the anterior belly of the digastric; it also 
supplies sensory branches as follows: the temporalis superficialis, the buc- 
cinatorius, the lingualis and sublingualis, the rami dentales and mentales. 
The N. ophthalmicus divides into three branches, viz., the N. frontalis, the 
N. lacrimalis and the N. nasociliaris. The N. maxillaris supplies the follow- 
ing branches: N. orbitalis, N. infraorbitalis, Nn. palatinus major and minor 
and the N. sphenopalatine. 

N. oculomotorius. III. Motor. 

This nerve supplies all the extrinsic muscles of the eye except the obliquus 
dorsalis or trochlearis, the rectus externus and the retractor oculi. The 
superficial origin of the nerve is from the crus cerebri. It passes from the 
cranial cavity through the foramen lacerum orbitale and is here covered by 
the three branches of the N. ophthalmicus. At the apex of the orbit the 
nerve divides into a small dorsal branch and a much larger ventral branch, 
PI. V, 33, 34. The dorsal branch is short and supplies the muscles rectus 
dorsalis and levator palpebrae dorsalis. It enters the rectus dorsalis about 
two centimeters from the origin of the muscle and near its lateral border. 
The very small filament to the levator palpebrae dorsalis may be found best 
by raising somewhat the latter muscle from the rectus dorsalis and carefully 
removing the intervening connective tissue. The filament enters the muscle 
at its inner or deep face near the middle of the muscle. By using a magnifier 
the filament may easily be recognized and traced to its place of origin from 
the dorsal branch of the N. oculomotorius. Usually it is more or less 
embedded in the M. rectus dorsalis. The ventral branch of the N. ocu- 
lomotorius is much larger and longer than the dorsal branch. Before 
attempting to follow this ventral branch, which passes between the tendons 
of origin of the rectus dorsalis and rectus externus, first dissect the branch 
of this nerve that supplies the M. obliquus ventralis. This branch lies 
between the adjacent borders of the external and ventral recti muscles, 
PI. IV, 29. Trace it to its termination in the ventral oblique muscle. 
Transect the M. rectus externus near its middle and reflect the proximal end. 
Now follow the branch that supplies the M. obliquus ventralis to its place of 
origin from the ventral branch of the oculomotor, taking care not to disturb 



26 

the small ciliary ganglion which lies close to the place of origin of this branch 
from the oculomotor, PI. V, 38. Usually the ciliary ganglion is so small 
that it cannot be seen clearly with the unaided eye ; by using a magnifying 
glass, however, it can be seen satisfactorily. Near the origin of the branch 
to the M. obliquus ventralis the ventral branch of the N. oculomotorius 
terminates in several large short branches of which two or three enter the 
rectus ventralis and one or more equally large branches enter the rectus 
interims, PI. V. No special dissection is necessary to demonstrate the 
large branches just mentioned. 

Ganglion ciliare (Ophthalmic ganglion). 

This small ganglion lies directly against the ventral branch of the N. 
oculomotorius and is connected to it by one or more very short branches from 
that nerve, which branches constitute the motor or short ciliary root of the 
ganglion (radix brevis ganglii ciliaris ) . The sensory or long ciliary root of the 
ganglion (radix longa ganglii ciliaris) is formed by a branch from the N. 
nasociliaris, PI. V, t,2. From the ciliary ganglion and its sensory root 
are given off the several ciliary nerves which accompany the optic nerve to 
the globe of the eye. [The ganglion is more easily demonstrated in the 
cat than in the horse.] 

N. abducens, VI. Motor. PI. VI, 13. 

The superficial origin of the N. abducens is from the medulla, immediately 
posterior to the pons. It passes from the cranial cavity into the orbit 
through the foramen lacerum orbitale and divides into two branches the 
larger of which enters the M. rectus externus at its inner face, near the origin 
of the muscle. The smaller branch enters the M. retractor oculi, a short dis- 
tance from its origin, and is the only nerve supplied to this muscle, PI. V, 36. 

N. trochlearis or patheticus, IV. Motor. 

The superficial origin of the N. trochlearis is from the anterior medullary 
velum immediately posterior to the quadrigemina. It passes through the 
smallest of the three suprasphenoidal grooves and emerges from the cranial 
cavity through the foramen patheticum, PI. IV, 24, and PL V, 31. The 
nerve extends from this foramen directly to the M. trochlearis or obliquus 
dorsalis which it enters at its dorso-lateral border at a point about half-way 
between the place of origin of the muscle and the trochlea or pulley through 
which the muscle passes. 



27 

N. acusticus, VIII. Sensory. 

The apparent origin of this nerve is from the side of the medulla imme- 
diately caudal to the N. facialis, PI. VI, 15. Its real origin, however, 
is from the spiral and vestibular ganglia of the internal ear. It passes 
through the internal auditory meatus with the N. facialis. 

Submaxillary salivary gland. 

To expose this organ, transect the M. pterygoideus internus just ventral 
to the N. lingualis and remove the detached portion of muscle. Turn the 
M. stylomandibularis dorsally. The submaxillary salivary gland extends 
from beneath the wing of the atlas to the basihyoid or body of the hyoid 
bone. It is from 20 to 25 cm. in length and from 2 to 4 cm in width, al- 
though the cervical or posterior end is sometimes much wider. The gland is 
somewhat crescent shaped and is surrounded by a thin fibrous capsule. Turn 
the gland dorsally noting meantime any small arteries supplied to it. Trace 
its duct, which extends along the deep face of the gland nearly the whole 
length of the organ and is continued anteriorly to the caruncula sublingualis 
where it opens into the oral cavity. 

Nerve filament to the M. stylohyoideus. 

This very small filament extends along the outer face of the proximal por- 
tion of the M. stylohyoideus for a distance of several centimeters. Trace 
the filament to its place of origin from the N. facialis, PI. Ill, 77. 

Exposure of the A. carotis communis. 

Remove the aponeurosis covering the V. jugularis and the adjoining 
muscles. Turn aside the M. sterno-mandibularis taking care not to cut the 
nerve that enters its deep face at the level of the V. maxillaris externa. Now 
turn aside the M. subscapulo-hyoideus in order to expose the trachea, the 
oesophagus (if on the left side) , the thyreoid body, the A. carotis communis 
and the common trunk of the vagus and sympathetic nerves, PI. 111,28,29, 
30, 36, 89. Spend some time in studying the relations to each other of the 
parts just mentioned. Note the relation of the thyreoid body to the angle 
formed by the jugular and external maxillary veins and also the relation of 
the jugular vein to the carotid artery. 

V. thyreoidea. 

This large vessel arises from the thyreoid body principally, but also from 
the superior cervical lymph gland and the posterior pharyngeal region, and 
terminates in the V. jugularis at nearly the same level as the V. maxillaris 
externa. Another vein from the muscles of the dorsal part of the neck enters 
the jugular at about this same level. 



28 

V. occipitalis. 

This large vein emerges from beneath the wing of the atlas and opens 
into the jugular about 5 cm. peripheral to the V. maxillaris externa. 

Anterior cervical lymph gland. 

This gland is situated in the triangular space formed by the jugular and 
external maxillary veins and the posterior border of the submaxillary salivary 
gland. The gland may form two or more separate masses the larger of 
which, six or more cm. in length in this specimen, lies at the side of the carotid 
artery; the smaller mass, 2 to 3 cm. in length, lies between the thyreoid 
body and the submaxillary salivary gland. This lymph gland is supplied 
with blood by a small branch from the A. thyreoidea superior. 

A. carotis communis, PI. Ill, 36. 

Trace this artery to the point where, under cover of the submaxillary 
salivary gland, it divides into its three terminal branches, viz., A. occipitalis, 
A. carotis interna and A. carotis externa, PL III. 38, 39, 40. 

Collateral branches of the A. carotis communis. 

(1) Several small branches to the oesophagus, the trachea and to some 
of the ventral muscles of the neck. 

(2) A. thyreoidea superior, PI. Ill, 37. 

This is the largest collateral branch of the A. carotis communis. It 
arises near the level of the thyreoid gland, bends over its cephalic end and 
terminates by several branches in the ventral surface of the gland; several 
large branches also enter the dorsal surface of the gland. It gives off a small 
pharyngeal branch to the posterior part of the pharynx and a larger laryngeal 
branch which passes between the cricoid and thyreoid cartilages to the 
interior of the larynx. 

(3) A. thyreoidea accessoria. 

In this specimen, the artery arises from the carotis communis 5 cm. pos- 
terior to the A. thyreoidea superior (10-12 cm. posterior to the trifurcation 
of the carotid). It soon divides into three or four branches of which the 
largest enters the posterior end of the thyreoid body ; the other small branches 
go to the muscles subscapulo-hyoideus, sterno-thyro-hyoideus and to the 
trachea. 

(4) A. parotidea. 

This artery is about the same size as the accessoria. It arises from the 
carotid at the same level as the thyreoidea superior and divides into two 



20 

branches of which one goes to the parotid gland and to the muscles brachio- 
cephalicus and rectus capitis anterior major; the other branch goes to the 
submaxillary salivary gland and to the muscles sterno-mandibularis and 
subscapulo-hyoideus and also supplies twigs to the cervical lymph gland. 

A. occipitalis. 

The origin of the A. occipitalis is from the carotis communis usually 
immediately peripheral to that of the A. carotis interna, PI. Ill, 38. Occa- 
sionally, however, these two arteries arise by a common trunk of variable 
length. The general course of the occipital artery is in nearly a direct line 
to the alar foramen of the atlas. Beneath the wing of the atlas the artery 
divides into two branches of which one passes through the alar foramen to 
the region of the poll and the other through the foramen transversarium of 
the atlas and anastomoses with the A. vertebralis. To expose the A. occipi- 
talis tuna aside the structures that cover the M. obliquus capitis posterior. 
Cut the latter muscle along its attachment to the wing of the atlas, taking 
care not to injure the arteries that pass through the foramen transversarium 
and the foramen alare. Free the muscle from its attachment to the atlas 
and the axis. Transect the M. obliquus capitis anterior close to its attach- 
ment to the wing of the atlas and also close to the styloid process and the 
crest of the occipital bone and turn it aside. Remove a portion of the wing 
of the atlas in order fully to expose the artery. 

Branches of the A. occipitalis. 

(1) A small branch to the posterior extremity of the submaxillary 
salivary gland (A. glandulae submaxillafis dorsalis). 

(2) Small branches to the ventral recti muscles of the head and to the 
parotid gland. 

(3) The A. condyloidea is a very small branch which can be traced, at 
present, for only a short distance. It divides into very small muscular and 
meningeal branches. The former go to the muscles rectus capitis anterior 
major and minor. The two very small meningeal branches enter the cranial 
cavity by the foramen lacerum basis cranii and the hypoglossal foramen 
respectively, and are distributed to the dura. 

(4) A. meningea posterior. 

This branch is much larger than any of the preceding branches. It runs 
along the posterior edge of the styloid process of the occipital bone, passes 
through the mastoid foramen (trace it only to this foramen) and is distrib- 
uted to the dura. Near the base of the styloid process it gives off a branch 
to the region just posterior to the occipital tuberosity. 



30 

(5) Ramus caudalis (retrograde). 

This large branch leaves the A. occipitalis at nearly a right angle, passes 
through the foramen transversarium of the atlas and anastomoses with the 
A. vertebralis. 

(6) Ramus occipitalis. 

This large branch of the A. occipitalis passes through the alar foramen of 
the atlas and supplies the muscles and the skin in the region of the poll. In 
the alar groove it gives off the A. cerebro spinalis which passes through the 
intervertebral foramen of the atlas, penetrates the dura and divides into 
two branches, ramus cerebralis and ramus spinalis. These two branches 
will be demonstrated after removing the brain, PI. VI. 

Pharyngeal lymph glands, PI. Ill, 31. 

These glands lie directly ventral to the M. stylohyoideus and are covered 
laterally by the muscles stylo-mandibularis and digastricus. They often con- 
sist of two groups : The larger and more compact group lies on the lateral 
surface of the pharynx along the course of the A. carotis externa. The 
smaller group, posterior or retropharyngeal lymph gland, is situated 
between the posterior face of the pharynx and the eustachian or guttural air 
sac. It consists of more or less isolated or scattered lymph nodules. 

A. carotis interna, PL III, 39; PI. VI, 27. 

This artery is one of the three terminal branches of the carotis communis. 
It extends to the foramen lacerum basis cranii through which it passes into 
the cranial cavity. Its distribution to the brain will be demonstrated after 
the removal of that organ. 

A. carotis externa, PI. Ill, 40. 

The A. carotis externa is the largest of the three terminal branches of the 
carotis communis. It crosses the lateral wall of the pharynx at the caudal 
border of the eustachian or guttural air sac and is covered by the submaxil- 
lary salivary gland, the muscles stylo-mandibularis, digastricus, stylohy- 
oideus and the N. hypoglossus. Upon emerging from beneath these struc- 
tures the artery passes more or less obliquely across the stylohyoid or great 
cornu of the hyoid, and near its dorsal border divides into two terminal 
branches: A. temporalis superficialis and A. maxillaris interna, the latter 
being much the larger, PI. Ill, 48, 31. The collateral branches of the ca- 
rotis externa are three in number, viz., A. maxillaris externa, A. masseter- 
ica, and A. auricularis posterior, PI. Ill, 41, 46, 47. 



3i 

(1) A. maxillaris externa. 

The A. maxillaris externa rises from the carotis externa either on the inner 
surface of the posterior belly of the M. digastricus or on the inner surface of 
the M. stylohyoideus. In the first part of its course the artery crosses the 
lateral wall of the pharynx nearly parallel to the stylohyoid bone and is 
covered by the muscles digastricus and stylohyoideus. The N. hypoglos- 
sus lies immediately ventral to the artery, PI. III. After giving off the large 
A. lingualis from its dorsal side (PL III, 43) the vessel inclines ventrally, 
crosses the N. hypoglossus, the intermediate tendon of the digastricus where 
the latter plays through the tendon of the stylohyoideus, the submaxillary 
duct and often the end of the submaxillary gland itself, and enters the sub- 
maxillary space near the posterior end of the submaxillary lymph gland. In 
the submaxillary space the artery lies between the V. maxillaris externa and 
the submaxillary lymph gland. The remaining or facial portion of the 
A. maxillaris externa has already been dissected (p. 12). Three col- 
lateral branches arise from the A. maxillaris externa between its point of ori- 
gin and the anterior extremity of the submaxillary salivary gland, viz., A. 
palatina ascendens, A. lingualis and A. sublingualis. In addition to these 
three collateral branches several small twigs are supplied to the M. ptery- 
goideus internus, the anterior extremity of the submaxillary salivary gland 
and the pharyngeal lymph gland. 

(a) A. palatina ascendens, PI. Ill, 42. 

This artery arises from the dorsal side of the A. maxillaris externa 2 to 4 
cm. from the A. carotis externa : sometimes, however, it arises in the angle 
formed by the carotis externa and the maxillaris externa. It passes beneath 
the stylohyoid bone, a short section of which should be removed, and is dis- 
tributed to the lateral wall of the pharynx, the soft palate and the tonsil. 

(b) A. lingualis, PI. Ill, 43. 

This large artery diverges from the maxillaris externa at the tip of the 
thyroid cornu of the basihyoid, extends along the ventral edge of the stylo- 
hyoid for a short distance and then dips under the M. hyoglossus. Before 
exposing the artery first trace the large N. hypoglossus, which lies just ventral 
to the A. maxillaris externa, across the lateral face of the M. hyoglossus. 
Now push aside the M. styloglossus, PI. Ill, 12, in order more fully to expose 
the M. hyoglossus (PI. Ill, 13), and transect the latter muscle one to two 
centimeters dorsal to the N. hypoglossus. Separate the M. hyoglossus 
from the more deeply lying genioglossus and trace the artery to the tip of the 
tongue. (Occasionally the A. lingualis lies on the superficial face of the 
M. hyoglossus as in the specimen from which Plate III was made). 



32 

(c) A. sublingualis, PI. Ill, 44. 

This is a smaller vessel than the preceding. It arises from the maxillaris 
externa at the anterior or cephalic extremity of the submaxillary salivary 
gland, passes anteriorly on the inner face of the anterior belly of the M. 
digastricus, and between the ramus of the mandible and the M. mylohy- 
oideus to near the middle of the latter muscle; here it pierces the mylohy- 
oideus, runs along the inner surface of the sublingual gland and terminates 
in the mucous membrane of the anterior portion of the floor of the mouth. 
Just as the artery passes through the mylohyoideus it gives off a branch, 
A. submentalis, which runs on the outer surface of the M. mylohyoideus 
towards the lower lip and chin. The A. sublingualis supplies small branches 
to the mylohyoideus and digastricus, the sublingual gland and the submaxil- 
lary lymph gland. Occasionally a branch of considerable size arises from the 
maxillaris externa, near the place of origin of the A. sublingualis, crosses the 
lower border of the mandible and is distributed to the M. masseter. 

(2) A. masseterica. 

This artery originates from the A. carotis externa at the dorsal border 
of the M. stylohyoideus, PI. Ill, 46. One or two centimeters from its 
origin it divides into a superficial and a deep branch. The superficial branch 
is distributed to the parotid gland and the M. masseter; the deep branch 
to the muscles pterygoideus internus, stylomandibularis and the posterior 
belly of the digastricus. 

(3) A. auricularis posterior (continued). 

The A. auricularis posterior arises at a very acute angle from the A. carotis 
externa about one centimeter peripheral to the A. masseterica, PI. Ill, 47. 
It extends dorsally towards the base of the ear and is deeply covered 
by the parotid gland to which it sends numerous small branches. The 
two superficial branches have already been dissected (p. 9). The deep 
branch arises 1 to 2 cm. from the origin of the parent trunk, and after 
giving off a small branch to the tympanum or middle ear, passes between 
the external auditory canal and the mastoid process of the petrous temporal. 
Transect the conchal cartilage and trace the artery as far as possible. 

A. temporalis superficialis. 

This is the smaller of the two terminal branches of the A. carotis externa, 
PL III, 48. After a course of 1 or 2 cm. it divides, under cover of the 
parotid gland, into two branches, the A. auricularis anterior and the A. 
transversa faciei, PI. II, 47, 48; PI. Ill, 49, 50. 



• 33 

(1) A. auricularis anterior. 

The artery auricularis anterior is accompanied by the vein and nerve of 
the same name and is deeply covered by the parotid gland to which it sends 
numerous small twigs. The vessel runs posterior to the capsule of the tem- 
poro-mandibular articulation and is distributed to the temporal and auricular 
muscles and the overlying skin. It sends a small branch to the inner 
surface of the conchal cartilage and also a branch which accompanies the 
N. auriculo-palpebraris to the supraorbital foramen where it anastomoses 
with the A. supraorbitalis. 

(2) A. transversa faciei. 

This artery has already been dissected. (See p. 13.) 

A. maxillaris interna, PL III, 51. 

The A. maxillaris interna is much the larger of the two terminal branches 
of the carotis externa and is the direct continuation of it, PL III, 51. It 
begins on the outer surface of the stylohyoid bone and extends in a tortuous 
course to the pterygoid or alar foramen of the sphenoid bone, passes through 
this foramen and the pterygo-palatine fossa, to the maxillary hiatus where it 
is continued by the A. palatina major. For convenience, the artery may be 
divided into three parts of which the first part, the longest and most tortuous, 
extends from the stylohyoid bone to the pterygoid or alar foramen of the 
sphenoid. The second part extends through the pterygoid or alar canal. 
The third part extends from the anterior extremity of the pterygoid or alar 
canal to the maxillary hiatus. The first part of the vessel describes an 
S-shaped curve and is covered by the M. pterygoideus externus. Beneath this 
muscle the artery is crossed superficially by the Nn. mylohyoideus, alveola- 
ris inferior, lingualis, pterygoidei, buccinatorius, and deeply by the chorda 
tympani. Note the relation of the artery to the eustachian or guttural air 
sac. The first part of the A. maxillaris interna gives off the following 
branches : 

(1) A. alveolaris inferior, PL III, 52. 

This arises from the convexity of the first curve of the A. maxillaris 
interna and with the vein and nerve of the same name passes through the 
alveolar canal of the mandible. At the mental foramen the artery anasto- 
moses with the A. labialis inferior and is continued to the lower lip as the 
A. mentalis. The alveolaris inferior supplies twigs to the pterygoid muscles 
and to the teeth and gums of the mandible ; the branch to the canine and 
incisor teeth accompanies the nerve that supplies these structures, as has 
already been demonstrated. 



34 

(2) A. tympanica, PI. Ill, 53. 

This small vessel arises a little peripheral to the preceding but from the 
opposite side of the A. maxillaris interna. It lies close to the common trunk 
of the nerves alveolaris inferior and lingualis (at the side of the chorda 
tympani) and enters the tympanum or middle ear. 

(3) Aa. pterygoideae. 

There are two or three of these small arteries. They arise from the 
concavity of the second curve of the maxillaris interna, PI. Ill, 55, and are 
distributed to the pterygoid and tensor palati muscles. 

(4) A. meningea media, PI. Ill, 54. 

The A. meningea media is a small artery which arises from the convexity 
of the second curve of the maxillaris interna, nearly opposite the pterygoid 
arteries and close to or even beneath the N. buccinatorius, PI. Ill, 54. 
Sometimes it arises in common with the A. temporalis profunda posterior. 
It can be traced but a short distance. It enters the cranial cavity by the 
foramen lacerum basis cranii and is distributed to the dura. 

(5) A. temporalis profunda posterior, PI. Ill, 56. 

This vessel arises from the dorsal side of the A. maxillaris interna a little 
before the latter enters the pterygoid or alar foramen. It is covered by the 
M. temporalis to which it is mainly distributed. (For some distance the 
artery accompanies the N. temporalis profunda posterior). 

The second part of the A. maxillaris interna, i. e., the part in the pterygoid 
canal, gives rise to two branches, A. temporalis profunda anterior and A. 
ophthalmica. These two arteries commonly originate by a very short com- 
mon trunk, PI. V, 17. 

(1) A. temporalis profunda anterior, PI. Ill, 57; PI. IV, 14; PI. V, 18. 
This artery, as just mentioned, arises from the second part of the A. 

maxillaris interna in common with the ophthalmica. It leaves the pterygoid 
canal by the temporal or alar parvum foramen and is distributed to the M. 
temporalis and the skin of the forehead. 

(2) A. ophthalmica, PI. V, 17. 

This artery originates from the A. maxillaris interna within the pterygoid 
canal in common with the A. temporalis profunda anterior. Upon emerging 
from the canal it enters the apex of the periorbita. Beneath the M. rectus 
dorsalis it makes a sharp curve and upon reaching the ethmoid fora- 



35 

men is continued by the A. ethmoidalis. (See laboratory specimen for the 
distribution of this artery.) The branches of the A. ophthalmica are as 
follows : 

(a) A. lacrimalis, PI. IV, 23. 

This small artery accompanies the N. lacrimalis to the lacrimal gland and 
upper eyelid. 

(b) A. supraorbitalis. 

This vessel arises either from the A. temporalis profunda anterior or the 
A. maxillaris interna. It pierces the periorbita between which and the 
osseous wall of the orbit it extends directly to the supraorbital foramen 
through which it passes and is distributed to the muscles orbicularis palpe- 
brarum and, corrugator supercilii and the skin of the forehead. 

(c) Rami musculares. 

The numerous muscular branches that supply the muscles of the eye. 

(d) Aa. ciliares. 

The numerous small ciliary arteries arise from the ophthalmica and its 
muscular branches. They are distributed to the ciliary body, the iris and 
the choroid coat of the eye. 

(e) A. centralis retinae. 

This is a small artery which supplies the retina. 

(f) A. ethmoidalis. (Trace this only to the ethmoid foramen). 

The A. ethmoidalis is the continuation of the ophthalmica. It passes 
through the ethmoid foramen into the cranial cavity and divides into 
meningeal and nasal branches, PI. VIII, fig. 2. The meningeal branch is 
distributed to the dura and anastomoses with the branches of the A. corporis 
callosi. The nasal branch passes through the cribriform plate into the nasal 
fossa and is distributed to the nasal mucous membrane. 

The third part of the A. maxillaris interna is shown in PI. IV. It extends 
from the anterior opening of the pterygoid canal to the maxillary hiatus. It 
gives off the following branches : 

(a) A. buccinatoria, PI. IV, 19; PI. II, 50; and PI. Ill, 58. 

The A. buccinatoria arises from the ventral side of the parent trunk soon 
after the latter emerges from the pterygoid canal. It crosses the maxillary 
tuberosity with the N. buccinatorius, and is distributed to the dorsal molar 



36 

glands and the muscles pterygoidei and buccinator. Near its origin the 
A. buccinatoria gives off a long slender branch (PI. IV, 16) to the large mass 
of orbital fatty tissue in the temporal fossa, posterior to the periorbita. 

(b) A. infraorbitalis, PI. IV, 17. 

The A. infraorbitalis arises from the dorsal side of the maxillaris interna, 
PI. IV, 17. It extends to the infraorbital canal, through which it passes, 
and continues to the canine and incisor teeth through the small osseous 
canal (canalis alveolaris incisivus) in the maxillary and premaxillary bones. 
Before entering the infraorbital canal it gives off the A. orbitalis, PI. IV, 18, 
which extends between the periorbita and the anterior wall of the orbit to 
the inner or nasal canthus of the eye and is distributed to the lower eyelid, 
the M. obliquus ventralis and the lacrimal sac. Within the infraorbital 
canal the A. infraorbitalis gives off small branches to the teeth and, at the 
infraorbital foramen, a branch of variable size which anastomoses with 
either the A. labialis dorsalis or the A. lateralis nasi. 

(c) A. palatina minor. 

This is a very small vessel which arises from the maxillaris interna, passes 
through the groove at the inner side of the maxillary tuberosity and is dis- 
tributed to the soft palate, PI. IV, 20. The N. palatums posterior and the 
palatine vein also pass through this groove with the artery. 

(d) A. sphenopalatina, PI. IV, 21; PI. V, 24. 

This vessel arises from the A. maxillaris interna at the extreme anterior 
part of the pterygo-palatine fossa, close to the orifice of the palatine canal, 
and passes through the spheno-palatine foramen into the nasal fossa where 
it divides into two branches. (See laboratory specimen). One of these 
branches is distributed to the mucous membrane of the nasal septum and 
the other to the mucous membrane of the inferior turbinal, the inferior 
meatus, the posterior nares and the maxillary and frontal sinuses. 

(e) A. palatina major. 

This artery is the direct continuation of the maxillaris interna. It passes 
through the palatine canal and groove with the N. palatinus anterior. At 
the incisive foramen it anastomoses with its fellow of the opposite side. 
From the arch formed by this anastomosis a branch passes through the 
incisive foramen and anastomoses with the dorsal labial arteries, PI. VII. 

N. glossopharyngeus, IX. Mixed. 

The superficial or apparent origin of the N. glossopharyngeus is from 
the medulla, PI. VI, 16. The deep or real origin of its motor fibers is from 



37 
two nuclei in the medulla. The sensory fibers arise from the cells of the 
ganglion petrosum of the nerve trunk. The centrally directed sensory 
fibers extend from the ganglion into the medulla. The peripherally directed 
sensory fibers supply in part the mucous membrane of the tongue, 
pharynx, the tympanic cavity and the eustachian tube. The glosso- 
pharyngeus passes through the foramen lacerum basis cranii with the 
Nn. vagus and accessorius, PI. Ill, 78. The nerve is readily found at 
any point along its course between the stylohyoid or great cornu of the hyoid 
and the A. maxillaris externa, PI. Ill, 84. It should not be mistaken for the 
much larger N. hypoglossus which runs parallel to it but which lies on the ven- 
tral side of the artery. Expose, as follows, the proximal portion of the nerve. 
With a chisel cut the paramastoid or styloid process of the occipital bone 
close to its base (PI. Ill, 3) and reflect it, with the portions of muscles 
attached to it, onto the stylohyoid. Trace the N. glossopharyngeus towards 
the base of the skull, noting its relation to the A. carotis externa and 
to the great N. hypoglossus, with which it is in close contact in this part of 
its course. Near the base of the skull these two nerves, together with the 
trunk of the vagus and sympathetic, are bound together by connective tissue 
into one large cord which is partially surrounded by a fold of the eustachian 
or guttural air sac. In exposing the nerves of this region it is not necessary 
to cut or tear the thin wall of this sac ; it may simply be pushed from around 
the nerves with the handle of the scalpel. At the base of the skull note the 
enlargement of the N. glossopharyngeus, the ganglion petrosum, PI. 

Ill, 79. A small nerve, N. tympanicus, originates from the antero-lateral 
face of the ganglion and extends dorsally, closely applied to the surface of the 
ganglion, into the tympanum or middle ear. Not infrequently some diffi- 
culty is experienced in demonstrating this small nerve; by using a magnifier, 
however, it can usually be seen without much difficulty, PL III, 80. The 
next branch of the N. glossopharyngeus is given off anywhere from 2 to 6 cm. 
before the main trunk crosses the A. carotis externa. This branch passes 
directly to the carotid nerve plexus at the trifurcation of the A. carotis com- 
munis. Very frequently this branch of the glossopharyngeus is joined by a 
branch from the superior cervical ganglion (PI. Ill, 93) of the sympathetic 
nerve shortly before reaching the plexus. As the N. glossopharyngeus 
crosses the medial surface of the A. carotis externa it divides into two nearly 
equal branches, ramus pharyngeus and ramus lingualis. 

(a) Ramus pharyngeus, PI. Ill, 82. 

Trace this branch to the place where it crosses, at a right angle, the 
stylohyoid bone and the M. stylopharyngeus. Note the small filament to 



3§ 

the M. stylopharyngeus, PL III, 83; this filament may originate from either 
the pharyngeal or the lingual branch of the N. glossopharyngeus. Opposite 
the place where the nerve crosses the stylohyoid and the M. stylopharyngeus, 
remove a section of the bone as shown in Plate III. Near the dorsal edge 
of the M. stylopharyngeus the nerve turns sharply and divides into numer- 
ous small branches which intermix with one of the pharyngeal branches of the 
vagus, as will be seen later, to form the pharyngeal plexus. The numerous 
branches of this plexus are distributed to the pharyngeal muscles and mucous 
membrane. 

(b) Ramus lingualis, PI. Ill, 84. 

This branch of the N. glossopharyngeus is somewhat larger than the 
pharyngeal branch and lies between the stylohyoid bone and the A. maxilla- 
ris externa as already mentioned. Turn aside the stylohyoid bone and trace 
the nerve peripherally. It gives several small branches to the isthmus of the 
fauces and the tonsil and terminates in the mucous membrane of the pos- 
terior third of the dorsum of the tongue. 

N. vagus, X. Mixed. 

The apparent or superficial origin of the vagus is from the ventro-lateral 
side of the medulla, Plate VI, 17. The deep or true origin, however, is as follows. 
The motor fibers arise within the medulla from the same mass of nerve cells 
that gives rise to the motor fibers of the glossopharyngeus. The sensory 
fibers arise from ganglion cells of the nerve trunk. The centrally directed 
sensory fibers terminate in the medulla. The peripherally directed sensory 
fibers are distributed to the mucous membrane of the larynx, trachea, 
lungs, oesophagus, stomach, intestines, gall bladder and gall ducts. The 
vagus passes through the foramen lacerum basis cranii in company with 
the N. accessorius or the eleventh cranial nerve. The two nerves appear as 
a single trunk for a distance of 2 to 5 cm. from the base of the skull; they then 
separate and the great N. hypoglossus passes between them, PI. Ill, 92, 
the vagus being medial and .the N. accessorius lateral to the hypoglos- 
sus, PI. Ill, 85. Trace the vagus for some distance along the course of the 
carotis interna and carotis communis noting that near the trifurcation of the 
carotis communis the vagus becomes closely united to the N. sympathicus, 
PI. HI, 95. 

(1) Pharyngeal branch of the N. vagus, PI. Ill, 86. 

The pharyngeal branch of the vagus is given off opposite the superior 
cervical ganglion of the sympathetic (PI. Ill, 86, 93) and soon divides into 
two nearly equal branches. I'] x m drawing the carotid artery and the vagus and 



39 

the sympathetic nerves somewhat ventrally, one of these branches may be 
traced to its place of distribution to the pharyngeal muscles and the pharyn- 
geal extremity of the oesophagus. The other branch of the pharyngeal 
nerve passes deeply between the eustachian or guttural air sacs, and is more 
difficult to follow ; however, by pushing aside the walls of the sacs the nerve 
may be traced to the dorso-lateral wall of the pharynx near to the insertion 
of the M. stylopharyngeus, PI. Ill, 10, where it divides into numerous 
branches some of which intermix with the pharyngeal branch of the N. 
glossopharyngeus, the two together forming the pharyngeal plexus, as 
already mentioned. 

(2) N. laryngeus superior, PI. Ill, 87; PI. IX, 25. Sensory. 

The large N. laryngeus superior arises from the vagus about 6 cm. from 
the point where the vagus and hypoglossus cross each other, PI. Ill, 87. 
At the place where the laryngeus superior leaves the trunk of the vagus is 
sometimes an indistinctly marked network called the ganglion nodosum.The 
N. laryngeus superior crosses the medial face of the Aa. carotis externa and 
interna, near their origin, and enters the larynx through the foramen near 
the cephalic border of the thyreoid cartilage. The nerve is distributed to the 
mucous membrane of the larynx, the floor of the pharynx and the entrance to 
the oesophagus. A very small branch, sometimes called the N. laryngeus 
externus or medius, is given off either from the plexiform enlargement of the 
vagus (ganglion nodosum) or more commonly from the N. laryngeus superior 
and extends directly to the M. cricothyreoideus ; it also supplies a small fila- 
ment to the M. cricopharyngeus. 

(3) N. laryngeus inferior or recurrens. 

The origin and course of the N. laryngeus inferior can not be seen until 
the thoracic portion of the vagus is dissected. Its distribution to the muscles 
of the larynx will be taken up later. 

N. accessorius, XL Motor. 

The nucleus of origin of this nerve is very elongated. It begins near 
the middle of the medulla and extends caudally nearly the whole length of 
the cervical portion of the spinal cord. The radicles of the nerve emerge 
from the spinal cord and medulla and together make up the nerve trunk. 
The nerve trunk begins between the sixth and seventh cervical spinal nerves 
and extends cephalad along the immediate lateral face of the spinal cord. 
It passes between the dorsal and ventral roots of the first six spinal nerves 
and is enclosed by the dura and arachnoid of the spinal cord, PL VI, 18. 
In this ascending course the nerve gradually increases in size as it at in- 



4 o 

tervals receives additional filaments from the spinal cord. After entering the 
cranial cavity the nerve receives some filaments from the medulla. The N. 
accessorius accompanies the vagus to the foramen lacerum basis cranii and 
for a short distance from the base of the skull , as already noted , PI . 1 1 1 , 90 . After 
leaving the vagus the nerve passes across the lateral surface of the eustachian 
or guttural air sac and the ventral surface of the wing of the atlas and finally 
gains the dorsal border of the M. brachiocephalicus along which it extends 
nearly the entire length of the neck. The distribution of this portion of the 
nerve is principally to the thoracic portion of the muscle trapezius ; one or 
more small branches, however, are supplied to the cervical portion of the 
trapezius and to the muscle brachiocephalicus. Shortly after crossing the 
A. occipitalis the N. accessorius sends off a large branch to the muscle sterno- 
mandibularis, PI. Ill, 91. In its course along the neck the nerve is joined 
by branches from the ventral divisions of the first six cervical nerves. 

N. hypoglossus, XII. Motor. 

The superficial origin of the N. hypoglossus is from the medulla, PI. VI, 
19. It passes through the hypoglossal foramen and between the vagus and 
accessorius, PI. Ill, 92. The hypoglossus crosses the lateral face of the A. 
carotis externa, at the place of origin of the A. maxillaris externa, and then 
extends along the ventral side of the latter vessel as far as to the ceratohyoid 
of the hyoid; from this point it extends between the muscles mylohyoideus 
and hyoglossus to about opposite the tip of the lingual prolongation of the 
basihyoid, a distance of 8 to 10 cm., where it divides into a superficial and a 
deep branch. The smaller superficial branch supplies the muscles stylo- 
glossus and hyoglossus. The larger deep branch of the hypoglossus crosses 
the ventral edge of the M. hyoglossus and extends obliquely between this 
muscle and the M. geniohyoglossus toward the tip of the tongue. In this 
intermuscular course the nerve divides into many branches which are distrib- 
uted to the muscles of the tongue. Near the point where the N. hypoglos- 
sus divides into superficial and deep branches it gives off a small filament to 
the M. geniohyoideus. The N. hypoglossus communicates with the ventral 
division of the first cervical nerve by a small threadlike ramus which joins the 
hypoglossus just before the latter crosses the A. maxillaris externa or at any 
point intermediate to this and the base of the skull (PI. Ill, nerve just below 
31). The N. hypoglossus also gives off one or more small filaments which 
join the carotid plexus. 

N. laryngeus inferior (continued). PI. IX, 26. 

TheN. laryngeus inferior, of the left side, arises from the vagus within the 
thorax. It recurves around the arch of the aorta and in the first part of its 



4i 

course lies on the ventro-lateral face of the trachea; nearer the larynx the 
nerve lies on the dorso-lateral face of the trachea. In order to trace the 
terminal portion of the nerve, the pharyngeal muscles of the left side (or 
right side as the case may be) must be transected and turned aside. Near 
the posterior end of the M. cricoarytenoideus posterior is given off the 
branch to this muscle, entering at its deep face and near the lateral border of 
the muscle. Carefully trace the main trunk of the N. laryngeus inferior to 
the point where it passes beneath the thyreoid cartilage. Disarticulate the 
posterior cornu of the thyreoid from the cricoid and abduct the former suffi- 
ciently to expose the muscles crico-arytenoideus lateralis and thyro-arytenoi- 
deus. Near the middle of the lateral border of the M. crico-arytenoideus 
posterior a small branch is given off to the M. arytenoideus. This branch 
passes beneath the M. cricoarytenoideus posterior which should be tran- 
sected and turned aside, PI. IX. Beneath the thyreoid cartilage the laryn- 
geal nerve terminates in branches which supply the muscles cricoaryte- 
noideus lateralis, thyro arytenoideus and also one or more branches that 
anastomose with the N. laryngeus superior, PI. IX. All of these respective 
branches should be traced to their proper muscles. The N. laryngeus 
inferior of the right side recurves around the A. dorsocervicalis and is 
similarly distributed to the muscles of the right side of the larynx. 



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PLATE IV 

1. Cut surface of the supraorbital process. 

2. Frontal sinus. 

3. Cut surface of the zygomatic process of the temporal. 

4. Cut surface of the malar. 

5. Palpebrae. 

6. Gl. lacrimalis. 

7. M. rectus dorsalis or superior. 

8. M. levator palpebrae dorsalis or superior. 

9. M. rectus lateralis. 

10. M. rectus ventralis or inferior. 

11. M. obliquus ventralis or inferior. 

12. M. retractor oculi or bulbi. 

13. A. maxillaris interna. 

14. A. temporalis profunda anterior. 

15. A. supraorbitalis. 

16. Small artery to the mass of adipose tissue in the temporal fossa. 

17. A. infraorbitalis. 

18. A. orbitalis or malaris. 

19. A. buccinatoria. 

20. A. palatina posterior. 

21. A. sphenopalatina. 

22. Muscular branch of the A. ophthalmica. 

23. A. lacrimalis. 

24. N. trochlearis. 

25. N. supraorbitalis or frontalis. 

26. N. nasociliaris (palpebronasal). 

27. N. lacrimalis. 

28. N. orbitalis or zygomaticus. 

29. Branch of the N. oculomotorius to the M. obliquus ventralis. 

30. N. maxillaris. 

31. N. sphenopalatine. 

32. N. palatinus anterior or major. 

33. N. palatinus posterior or minor. 

34. Cut edge of the periorbita or ocular sheath. 



PLATE V 

1. Cut surface of supraorbital process. 

2. Frontal sinus. 

3. Cut surface of the zygomtic process of the temporal. 

4. Cut surface of the malar. 

5. Palpebrae. 

6. Gl. lacrimalis (somewhat reflected). 

7. M. rectus dorsalis or superior. 

8. M. levator palpebrae dorsalis or superior. 

9. M. rectus lateralis. 

10. M. rectus ventralis or inferior. 

11. M. rectus medialis. 

12. M. obliquus dorsalis or superior. 

13. M. obliquus ventralis or inferior. 

14. M. retractor oculi or bulbi. 

15. Cut edge of sphenoid. 

16. A. Maxillaris interna. 

17. A. ophthalmica. 

18. A. temporalis profunda anterior. 

19. A. supraorbitalis or frontalis. 

20. Small artery to the mass of adipose tissue in the temporal fossa. 

21. A. infraorbitalis. 

22. A. orbitalis or malaris. 

23. A. buccinatoria. 

24. A. sphenopalatina. 

25. N. Maxillaris cut and one end turned aside. 

26. N. lacrimalis, cut and turned aside. 

27. N. supraorbitalis or frontalis. 

28. N. nasociliaris or palpebronasal. 

29. N. ethmoidalis. 

30. N. infratrochlearis. 

31. N. trochlearis. 

32. Srnsory root of Gang, ciliare. 

33 and 34. N. oculomotorious, dorsal and ventral branches. 

35. Small branch from the N. oculomotorious to the M. levator palpe- 

brae dorsalis. 

36. N. abducens. 

37. N. orbitalis or zygomaticus (the peripheral portion has been removed). 

38. Ganglion ciliaris. (Represented too large] 

39. Nn. ciliares. 

40. N. opticus. 

41. N. sphenopalatinus. 

42. Ganglion sphenopalitinum showing many small nerves leaving it. 

43. N. palatinus anterior or major. 

44. N. palatinus posterior or minor. 

45. Cut edge of the periorbita or ocular sheath. 



PLATE VI 



1. Dura. 

2. Medulla. 

3. Cerebellum. 

4. Pons. 

5. Cerebrum. 

6. Hypophysis. 

7. Chiasma opticum. 

8. Bulbus olfactorius. 

9. N. opticus. 

10. N. oculomotorius. 

11. X. trochlearis. 

12. X. trigeminus. This trunk divides into three subdivisions, viz., 
12' X. ophthalmicus. 

12" X. maxillaris. 

12'" X. mandibularis 

13. X. abducens. 

14. X. facialis. 

15. X. acusticus. 

16. N. glossopharyngeus. 

17. X. vagus. 

18. X. accessorius. 

19. X. hypoglossus. 

20. First spinal nerve. 

21. A. cerebrospinalis. 

22. A. spinalis ventralis. 

23. A. basilaris. 

24. A. cerebelli posterior. 

25. A. carotico-basilaris. 

26. A. cerebelli anterior. 

27. A. carotis interna. 

28. A. intercarotica. 

29. A. cerebri profunda. 

30. A. choroidea anterior. 

31. A. communicans posterior. 

32. A. cerebri media. 

33. A. cerebri anterior. This either fuses with its fellow of the opposite 
side as in the present case, or is joined to it by a transverse branch 
called A. communicans anterior. 

34. A. meningea anterior. 

35. A. corporis callosi. 

36. A. ethmoidalis See PI. VIII, fig. 2. 

37. Xasal branch of the A. ethmoidalis. See PI. VII, fig. 2. 




CWRedwood 



PLATE VI a. 



1 (PI. VI, 21 ) A. cerebrospinalis. 

2 (" ", 22) A. spinalis ventralis. 

3 Rami medullares. 

4 4(P1. VI, 23) A. basilaris. 

5 (PI. VI. 24) A. cerebelli posterior. 

6 (" " 25) A. carotico-basilaris. 

7 ( " " 27) A. carotis interna. 

8 ( " " 28) A. intercarotica. 

30) A. choroidea anterior. 

31) A. communicans posterior. 

32) A. cerebri media. 
( " " 33) A. cerebri anterior. 
( " " 34) A. meningea anterior. 
( " " 35) A. corporis callosi. 
( " " 29) A. cerebri profunda. 
A. cerebri posterior (Not named in PI. VI but are represented by the 

two small arteries immediately posterior to the hypophysis, No. 6). 
(PI. VI. 26) A. cerebelli anterior. 



9 ( 

10 ( 

11 ( 



PLATE VII 

FACIAL REGION IN PERSPECTIVE 

1. F. M. levator nasolabialis, cut and turned aside. 

2. M. levator labii superioris proprius. 

3. 3'. M. dilator naris lateralis, cut and turned aside. 

4. 4'. M. zygomaticus, cut and turned aside. 

5. M. masseter. 

6. M. buccinator. 

7. M. depressor labii infcrioris. 

8. M. cutaneous faciei. 

9. A. maxillaris externa. 

10. A. labialis ventralis or inferior 

11. A. labialis dorsalis or superior. 

12. A. lateralis nasi. 

13. Small artery to nasal region. 

14. A. dorsalis nasi. 

15. A. angularis oculi. 

16. Terminal branches of the A. palato-labialis. These branches anas- 

tomose with the dorsal nasal and the superior labial; they also give 
off branches to the upper lip and the nostrils. 

17. V. maxillaris externa. 

18. N. facialis. 

19. N. infraorbitalis. 

20. Ductus parotideus. 

21. Tongue. 

22. Caruncula sublingualis. 



sr i^i\ i c v 1 1 




PLATE VIII 



FIGURE i. 

1. Naris. 

2. Tongue. 

3. Mandible. 

4. M. zygomaticus. 

5. M. buccinator (a portion of this muscle has been removed to show 

the sublingual salivary gland). 

6. M. masseter. 

7. 7'. M. depressor labii inferioris. 

8. Glandula sublingualis with its numerous ducts which open into 

the oral cavity. 

9. A. maxillaris externa. 

10. A. labialis ventralis or inferior. 

11. A. angularis oris. 

12. V. maxillaris externa. 
•3- 13', 13". Vv. labiales. 

14. Ductus parotideus. 

15. N. buccinatorius. 

16. N. alveolaris inferior. 



FIGURE 2. 

1. Frontal sinus. 

2. Ethmoid bone. 

3. Fossa ethmoidalis. On the right side a portion of the frontal bone has 
been removed in order to show the extent of the ethmoid fossa and 
the blood vessels in it. 

4. Portion of falx cerebri. 

5. A. communicans posterior. 

6. A. cerebri media. 

7. A. cerebri anterior. 

8. A. corpus calosi. 

9. A. meningea anterior. 

10. A. ethmoidalis. 

11. 11', Rete ethmoidale. 

12. Nasal branches of A. ethmoidalis. 

13. Chiasma opticum. 

14. Part of hypophysis. 



PLATE VIII 




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